The unifying theme of this PPG renewal is understanding the pathophysiology, and establishing the optimal management, of two of the most serious and frequently encountered conditions among critically ill, premature infants: anemia and thrombocytopenia. Current treatment for these conditions relies largely on transfusion of red blood cells and plateletstherapies that remain controversial and incompletely investigated. Prior research by our PPG group and others has established that many aspects of the pathophysiology of the anemia and thrombocytopenia of prematurity are unique. However, our understanding is incomplete. Hence, the goals of our renewal are to further define the mechanisms that give rise to these pressing and related clinical conditions, to optimize their treatment per such mechanistic knowledge, and consequently, to reduce both short- and long-term disabilities associated with these conditions. Our 4 interrelated projects, whose objectives are directly relevant to our unifying theme, include: Project 1 Optimized erythropoietin treatment of neonatal anemia, PL JA Widness (and P Veng-Pedersen); Project 2 Pathogenesis and treatment of neonatal thrombocytopenia, PL M Sola-Visner; Project 3 Preterm transfusions: brain structure/function outcomes, PL PC Nopoulos; and Project 4 The role of neonatal anemia In learning and memory, PL MK Georgieff. Core A (Administrative, statistical, and research personnel) and Core B (Laboratory and database, PL DM Mock) will provide support for all projects. To enhance effectiveness, our program has expanded to involve four (vs. two) performance sites, so that data can be shared among Projects 1, 2 and 3 (i.e. data from the same infants will be used In studies at multiple sites). Our history of success conducting multisite research will be invaluable in coordinating studies across the various performance sites. Because our Program rests on a highly-qualified, multidisciplinary group of new and experienced investigators, our renewal program consists of unique and collaborative research teams capable of accelerating the acquisition of knowledge vital to the fields of neonatal anemia and thrombocytopenia. Over the past 17 years, our productive PPG group (200 publications) has made a substantial impact on clinical practice and research in neonatal transfusion medicine and hematology. Our program embraces and exemplifies the synergistic P01 approach, which has and will enable us to make more rapid progress than any of us could individually. With this renewal, we are poised to continue to challenge paradigms and advance knowledge, as we build on prior results and maximize collaboration.